1. Field of the Invention
The present invention relates to a mechanism for pressing a nozzle of an injection device against a die.
2. Background Art
A mechanism for pressing a nozzle of an injection device against a die is disclosed in, for example, Japanese Examined Utility Model (U.M. Kokoku) No. 35-7978. U.M. Kokoku No. 35-7978 discloses a nozzle pressing mechanism in which one or two or more hydraulic cylinder devices are attached, via ball joints, to opposite surfaces of an injection device portion (a heating cylinder attaching surface) provided with an injection nozzle and a die attaching plate. Accordingly, even when the axis of the injection device is inclined from a horizontal position to adjust the abutment between the injection nozzle and the die, the axial direction of the hydraulic cylinder device can be easily changed and adjusted in accordance with variations of the axial direction of the injection device. Thus, this mechanism can be conveniently used. However, this mechanism protects only the hydraulic cylinder device. Namely, when the abutment between the injection nozzle and the die is adjusted as described above, the portion of the die, against which the injection nozzle is abutted is changed and, accordingly, a distance between the portion of a die attaching plate, to which the hydraulic cylinder device is attached, and the portion of the die, against which the injection nozzle is abutted, varies as shown in FIG. 5. Thus, the direction of pressure of the injection nozzle applied to the die by the hydraulic cylinder device is deviated from the axis of the injection nozzle (injection device). Consequently, a component force is applied to the injection nozzle in a direction perpendicular to the axis of the injection nozzle and, accordingly, molten material may leak through a gap between contact surfaces of the injection nozzle and the die, or the contact surface of the injection nozzle or the die may be damaged.
The heating cylinder is downwardly bent, due to its weight, because the injection nozzle is attached to a front end of the heating cylinder extending in an axial direction thereof and being heavy. Accordingly, the direction of pressure of the injection nozzle applied to the die by the hydraulic cylinder device is deviated from the axis of the injection nozzle (injection device). The occurrence of this phenomenon is more remarkable as the size of the injection device is increased. A component force is applied to the injection nozzle in a direction perpendicular to the axis of the injection nozzle in a manner similar to the above. Thus, the molten material may leak through a gap between contact surfaces of the nozzle and the die, the contact surface of the nozzle or the die may be damaged, and the degree of curve of the heating cylinder may be increased.